The water flow from marine propulsion jets tends to be turbulent and difficulty is experienced in coordinating the seal around its edges when in the reverse steering mode. It is not only the directed axis of the jet but the turbulence which results in diverging spray which is thrown upward in the form of a "rooster tail" that interferes with skiers and accounts for a slight thrust loss. And the reverse mode must be cooperatively related to the forward mode and both steerable, without being subject to jamming in the presence of sand and mud or other debris. It is a general object therefore, to match the nozzle with the cross sectional configuration of the pump exit, both with respect to flow in the forward mode and to seal when in the reverse mode.
It is a primary object of this invention to supress spray that is normally thrown upward from jet nozzles. Heretofore, exit passage and nozzle design has not been altogether compatable with the steering function, and nozzles have not been perfect continuations of the pump exit passage. For example, the usual exit nozzle configuration is that of a cylindrical tube, the nozzle being on a swivel so as to turn from side to side, but without any means embodied in the nozzle per se to supress the jet. With the present invention turbulence and upward diversion of spray is supressed by providing a flattened exit passage and correspondingly shaped nozzle, both matched with respect to the side walls thereof, and particularly with respect to the top wall thereof. By matching the plane of the top walls of the exit passage and nozzle passage, the thrust flow remains perfectly straight and level, without thrust losses and reducing the turbulence so that upward divergence of the jet is substantially eliminated.
It is also an object of this invention to seal around the jet nozzle when in the reverse mode, and all without being subject to jamming. Heretofore, reverse gates have been cylindrical or spherical, and actuable about a centered axis or pivot point. Consequently, sliding motion between closely fitting parts has been characteristic, resulting in reverse gates that are vulnerable to the presence of any foreign matter. Replacement of the rotative center has been proposed but is not satisfactory alone, since hydraulic pressure in the reverse mode forces the gate open. Therefore, it is an object herein to relocate the center of curvature of the side seals, heretofor concentric with rotation but now eccentric thereto. As a result, hydraulic pressure does not tend to open the gate and there is no adverse reaction on the control system therefor. The seals have line contact, with an angular separating motion rather than a sliding motion.